In treating diseases caused by abnormal tissue growth that is dependent upon a certain sexual steroidal hormone such as estrogen, it is highly important to significantly inhibit, more preferably completely eliminate, the effect induced by the hormone. For this purpose, it is desirable to reduce the level of hormone capable of acting on the steroidal hormone receptor site. For instance, anti-estrogenic agents are commonly administered for alternative or combination therapy to limit the production of estrogen to the amount less than required to activate the receptor site. However, such conventional technique for blocking estrogen production could not sufficiently inhibit the effect induced through the estrogen receptor. Practically, even when estrogen is completely absent, some of the receptors may be activated. It was therefore considered that estrogen antagonists could provide better therapeutic effect in comparison to the technique for blocking only the production of sexual steroidal hormone. Thus, numerous estrogen antagonists have been developed. For example, many patent publications including U.S. Pat. Nos. 4,760,061, 4,732,912, 4,904,661, 5,395,842 and WO 96/22092 disclose various anti-estrogenic compounds. Sometimes, however, prior art antagonists may themselves act as agonists, and therefore activate rather than block the receptor. For example, Tamoxifen has been most widely used as an anti-estrogenic agent. However, this agent has a disadvantage that it exhibits estrogenic activity in some organs (see, M. Harper and A. Walpole, J. Reprod. Fertile., 1967, 13, 101).
As another non-steroidal anti-estrogenic compound, WO 93/10741 discloses a benzopyran derivative having an aminoethoxyphenyl substituent(s) (Endorecherche), the typical compound of which is EM-343 having the following structure:
Said compound also has the agonistic effect. It is therefore required to develop an anti-estrogenic compound which is substantially or completely free of agonistic effect and which can effectively block the estrogen receptor.
In addition, it has been known that 7α-substituted derivatives of estradiol, for example, 7α-(CH2)10CONMeBu derivatives, are steroidal anti-estrogenic agents without agonistic effect (see, EP-A 0138504, U.S. Pat. No. 4,659,516). Further, an estradiol derivative having a 7α-(CH2)9SOC5H6F5 substituent has also been disclosed as a 7α-substituted derivative of estradiol (see, Wakeling et al., Cancer Res., 1991, 51, 3867).
Non-steroidal anti-estrogenic agents without agonistic effect have been first reported by Wakeling et al. in 1987 (see, A. Wakeling and Bowler, J. Endocrinol., 1987, 112, R7). Meanwhile, U.S. Pat. No. 4,904,661 discloses phenol derivatives having anti-estrogenic activity. These phenol derivatives generally have a naphthalene scaffold and include, typically, the following compounds:

Some chroman and thiochroman derivatives have been reported as anti-estrogenic compounds having no agonistic effect (WO 98/25916). Although the existing anti-estrogenic compounds having no agonistic effect show a substantial therapeutic effect when administered via intravenous or subcutaneous injection, they show a highly reduced therapeutic effect when administered orally, due to their low bioavailability by oral route. Therefore, for convenience's sake in the case of administration, it is desired to develop anti-estrogenic compounds which show a sufficient effect when administered orally and at the same time have no agonistic effect. Also, it is generally desired to develop agents which show a sufficient effect when administered orally.